A Mask Read Only Memory (Mask ROM) is a semiconductor memory device in which data is coded during a manufacturing process. There are various types of manufacturing processes to program a Mask ROM such as diffusion, metallization, and via processing. In diffusion processing, a Mask ROM is programmed during a diffusion process in a semiconductor substrate. In an embedded metal programmable ROM, ROM data is programmed during a metal/metallization process. In a via programmable ROM, which is similar to the embedded metal programmable ROM, ROM data code is programmed during a via forming process.